function get_newdate(n){
	var now = new Date();
	var date = new Date(now.getTime() - n * 24 * 3600 * 1000);
	var year = date.getFullYear();
	var month = date.getMonth() + 1;
	var day = date.getDate();
	var hour = date.getHours();
	var minute = date.getMinutes();
	var second = date.getSeconds();
	var end=year + '-' + month + '-' + day  + ' ' + hour + ':' + minute + ':' + second;
	return end;
}